The shrubby Persicaria amplexicaulis looks good wherever I see it. I have it in the garden (above) and a couple of weeks ago I came across it growing extensively round a lake in a San Fransisco park. Yet it originates in the Himalayas, China and Pakistan!
 Intense as they are the crimson red flower spikes seem to blend harmoniously with their surroundings and the stems and leaves have the toughness of a wild thing. Various cultivars are available, this one is either 'Firedance' or 'Firetail' I can't remember which (there's probably not much to choose between them). It prefers a bit of moisture but P. amplexicaulis is of the Knotweed family and these are very hardy plants; I can imagine it in some valley in the Himalayas.
 NB Several weeks ago [30th. June] I posted a photo of our native Persicaria bistorta which I saw by a babbling brook in Edale, it's different but clearly related.